Refers to any condition in which the deleterious effects are caused wholly or in part by components of the immune system.

IMMUNIZATION:

The administration of a vaccine in order to produce protective immunity against the infectious disease agent(s) present in the vaccine.

IMMUNOFLUORESCENCE ASSAY (IFA):

Assay technique for the detection of antigen or antibody using antibodies labeled with a fluorescent dye.

IMMUNOGLOBULINS (ANTIBODIES):

Specialized proteins produced by plasma cells (end-stage B lymphocytes) in response to the presence of foreign material (bacteria, viruses, toxins, etc.). Antibodies are capable of binding to the foreign material and thus alerting other immune cells to its presence. Often abbreviated Ig, there are five major classes: IgG, IgM, IgA, IgE, and IgD. In horses a subset of IgG known as IgG(T) is involved in the immune response to parasites and tetanus toxoid.

IMMUNOTHERAPY:

The use of medications that boost the immune response, to assist in the treatment of a disease.

IMPACTION COLIC:

Colic resulting in blockage of the intestine; can result from excessive consumption of grain or lush pasture, or ingestion of foreign material.

IN UTERO:

Within the uterus.

INACTIVATED ("KILLED") VACCINE:

A vaccine in which the infectious agent has been modified in some way (most often chemically) so that it no longer can infect and replicate within the host, but nevertheless is still capable of stimulating an immune response.

INAPPETENCE:

Lack of appetite; anorexia.

INCISIONAL BIOPSY:

Biopsy sample representing a portion of a larger lesion.

INCISIONAL HERNIA:

A defect in a healing incision wound that results in a bulging out of the underlying tissues.

INCISORS:

The front teeth.

INCONTINENCE:

Loss of voluntary control over urination or defecation.

INCUBATION PERIOD:

The time between exposure to an infectious disease agent and the onset of clinical signs of disease.

INDIRECT LIFE CYCLE:

With regard to parasites, a life cycle that can only be completed with the participation of an intermediate host.

INFARCT:

Localized tissue death resulting from obstruction of the blood supply to the affected site.

INFECTIVE STAGE:

The specific stage in the life cycle of a parasite that is able to initiate an infection in a definitive or intermediate host.

INFERTILITY:

Diminished ability to produce offspring.

INFLAMMATION:

Protective response, often localized, involving white blood cells and other components of the body, wherein a disease agent or other irritant factor is sequestered and attempts made to destroy it or neutralize its effects.

INGESTA:

Ingested food.

INGUINAL:

Pertaining to the groin area.

INGUINAL CANAL, INGUINAL RING:

An opening deep within the groin area for passage of the spermatic cord or the round ligament of the uterus.

INHALATION PNEUMONIA:

Pneumonia caused by inhalation of noxious fumes, as during a house or forest fire.

INNERVATION:

The distribution of nerves to a particular tissue or body part.

INSOLUBLE FIBERS:

Dietary fibers such as cellulose and wheat bran; they are good bulk-forming agents and are only poorly fermented (digested) by bacteria in the large intestine.

INSPIRATION:

The act of breathing air in; inhalation.

INSULIN:

Critically important hormone produced by the beta cells of the endocrine pancreas; responsible for regulating the blood concentration of glucose, the body's most important fuel molecule.

INSULIN-DEPENDENT DIABETES MELLITUS:

Diabetes mellitus characterized by an inability to utilize blood glucose because of inadequate amounts of circulating insulin.

INSULINLIKE GROWTH FACTORS:

Alternative name for somatomedins.

INTEGUMENT:

The skin.

INTERESTRUS:

Diestrus; the quiescent period between one heat period and the next.

INTERFERONS:

A specialized group of protein molecules capable of inhibiting virus replication and the growth of tumor cells, and of modulating the activities of certain components of the immune system.

INTERMEDIATE HOST:

A host that (usually) is essential to the life cycle of a parasite and in which the parasite undergoes development to juvenile but not mature stages.

INTERSEXUALITY:

Having characteristics of both sexes intermingling in the same individual.

INTERSTITIAL FLUID:

The fluid surrounding cells.

INTERVERTEBRAL DISKS:

Cartilaginous, cushioning structures positioned between the vertebrae of the spinal column.

INTOXICATION:

Poisoning.

INTRACRANIAL:

Within the skull.

INTRAMUSCULAR (IM):

A route of injection (into the muscle).

INTRAOCULAR PRESSURE:

The pressure within the eye.

INTROMISSION:

Insertion of the penis of the male into the vagina of the female during intercourse.

INTUBATION:

Insertion of a breathing tube into the trachea during anesthesia.

INTUSSUSCEPTION:

Prolapse ("telescoping") of one section of bowel into an adjoining section.

INVOLUTION:

Period of repair in which there is a return to normal size and composition, as of the uterus following birth and expulsion of the placenta.

IONIZE:

To separate into ions (charged atoms).

IONIZING RADIATION:

Radiation capable of ionizing matter; examples include X rays and radioactive isotopes of elements such as radon, cesium, and strontium.

IRIDOCYCLITIS:

Inflammation of the iris and ciliary body of the eye.

IRIS (PLURAL: IRIDES):

The circular, pigmented structure located behind the cornea; by expanding or contracting its central opening, or pupil, it regulates the amount of light penetrating the inner reaches of the eye.

IRRITANT CONTACT DERMATITIS:

Uncommon inflammatory skin disease caused by direct contact with an irritating concentration of an offending substance.

ISCHEMIC INJURY:

Injury caused by loss of blood supply to a tissue.

ISLETS OF LANGERHANS:

The endocrine cells of the pancreas; the beta cells within the islets of Langerhans are the source of the critically important hormone insulin.